Smoke simulator temperature decay
I assume that you use cycles render in blender.
If you used the quick smoke effect by adding Object/quick effects/ quick smoke you can try to set the color of the flame by: 


selecting the Smoke Domain of the fire emitting object 
open the node editor 
change the color of the flame in the ColorRamp settings.


Using more than one Smoke Domain means that you can have several color settings and combine then in your scene.